During the late 80s I worked as an illustrator for Nursing Times. When Margaret Thatcher's government split the NHS into self-governing trusts and created an internal market for services, I began a regular cartoon called "St Opt-Outs", an everyday story of medical folk struggling under the cosh of managers helicoptered in from the private sector. Adverts for life insurance printed on nurse's uniforms. Hot meals bussed in from Bulgaria. Anaesthetic stopping, mid-operation, when a patient's credit card maxed out.

Year by year it seemed less and less preposterous, because those changes were only the beginning of a relentless process, continued by every subsequent government, that led to the Health and Social Care Act of March last year.

If you don't know the contents and consequences of the act then you're not alone, and it's not your fault. This act will probably change our lives more than any other piece of legislation created by the present government. It was opposed by the British Medical Association and by all but one of the medical royal colleges. Yet it was never advertised in a manifesto. As Michael Portillo told Andrew Neil on BBC One's This Week in January 2011: "They did not believe they could win an election if they told you what they were going to do."

The bill itself is hard going and the media, who are justifiably up in arms about the shortcomings of individual hospitals, have been shamefully uninterested in what is being done to the healthcare system as a whole. Indeed, it was only when lawyers and academics started examining the act that the full implications became clear. This is the opening of an article in the British Medical Journal by professor Allyson Pollock, David Pryce and Peter Roderick:

"Entitlement to free health services in England will be curtailed by the Health and Social Care Bill currently before parliament. The bill sets out a new statutory framework that would abolish the duty of primary care trusts… to secure health services for everyone living in a defined geographical area".

And here is the opening of a report by Harrison Grant solicitors and the specialist barristers Stephen Cragg and Rebecca Haynes:

"The bill will remove the duty of the Secretary of State to provide or secure the provision of health services which has been a common and critical feature of all previous NHS legislation since 1946."

The NHS is founded on three fundamental principles. It is universal: everyone who needs medical treatment gets it. It is comprehensive: it covers all areas of healthcare. And it is free at the point of delivery.

The Health and Social Care Act has abolished the first principle – primary care trusts are no longer obliged to secure treatment for you or your children when you or they are ill. Because it gives unelected local bodies the power to close unprofitable local services, it effectively abolishes the second as well. And once those two principles are abolished, the third becomes irrelevant.

We know how this works because we've seen it happen with NHS dentistry. If you're well-off you go private. If you're poor and there are no NHS dentists in your area willing to take you on, then you simply don't have a dentist. Imagine this happening with oncology, or cardiac medicine, or care of the elderly.

If you feel strongly about this and live in Eastleigh then you should make your voice heard by voting for Dr Iain Maclennan and the National Health Action party on 28 February. This party comprise a group of doctors and health professionals who are fighting against what is, in effect, the destruction of the health service. The NHS we cheered during the opening ceremony of the Olympics. The NHS that recorded its highest ever level of public satisfaction in the annual British Social Attitudes Survey in 2010, when the present government came to power.

This is the most important issue in British politics at the moment, and they seem to be the only party who genuinely understand and care about what is happening.

We should be rightly proud of living in a society where every single person is entitled to good medical care and where no one is turned away. How will we explain to our children in 10 or 20 years' time that we did nothing to stop this precious and irreplaceable institution being taken from us?